Fig. 9. Differentiation of epithelial cells in conditional mutant lungs. Double in situ hybridization for Sftpc and Scgb1a1 in cre(-);Nmyc^flox/+ (A) and cre(+);Nmyc^flox/flox (B) lungs at E18.5. Note the paucity of type II cells in the mutant lung. (C,D) Immunofluorescence for Gp38 expressed on the apical surface of type I cells at this stage. Note the presence of attenuated presumptive type I cells lining the large sacs. (E) RT-PCR for Aqp5, SftpA and actin. Expression of Aqp5 is prematurely increased in cre(+);Nmyc^flox/flox lung at E16.5. Scale bars: 50 µm.